The present invention relates to a display apparatus for displaying a plurality of three-dimensional objects on a display as two-dimensionally displayed figures, and for showing precisely the positional relationship among the three-dimensional objects in a manner suitable, for instance, to robot simulation or the like.
Along with the advancement in robot technology, there have been developed various kinds of languages to control and manipulate robots. Computer robot language has frequently been used to simulate the behavior of a robot.
A robot's simulator displays the robot hands and the three-dimensional objects with which the robot is interacting. The robot's hands and objects are shown on the display as two-dimensional figures, and the motion of the robot hands is traced on the display. In the two-dimensional display of the three-dimensional objects, each object is treated as a projected figure or a perspective figure as seen from a certain line-of-sight. Accordingly, the user follows the behavior of the robot on the two dimensional display controlled by the robot language while inspecting the presence or absence of any connecting relationship indicated on the display, such as interference (collision) between objects that are displayed as two-dimensional figures.
However, when the projected views or perspective views are employed, the displayed positional relationship among the objects varies depending on the direction of line-of-sight. For this reason, the user can have difficulty in visualizing the interfering relationships among a plurality of objects, and whether or not the objects appear to be in contact or separated depends upon the direction of the line-of-sight.
Therefore, if a plurality of objects that are displayed as two-dimensional figures are seen as overlapping (when it is not clear whether or not there exists an interference), the user gives the command to change the direction of line-of-sight. Upon receipt of this command, the simulator obtains and displays a projected or perspective view of the three-dimensional objects as seen along a different direction of line-of-sight. However, the selection of the direction of line-of-sight is executed by the user on a trial and error basis. It is not unusual to change the line-of-sight many times until the user can determine whether interference exists among the objects. The prior art systems consequently have poor processing efficiency.
The general operation and programming of a robot is discussed in Kodaira et al., "Interactive Robot Programming with Real-Time Graphic Simulation," IECON'84, pp. 35-39.